Smoke eliminating apparatus



SMOKE ELIMINATING APPARATUS Filed June 18, 1947 4 Sheets-Sheet 1INVENTOR.

Co/vw/r Y /f/PCf 9 /WQZJQQ A TTORNEYS July 31, 1951 c. PIERCE I 5 5SMOKE ELIMINATING APPARATUS Filed June 18,. 1947 4 Sheets-Sheet 2INVENTOR. CONWAY IO/ERCE July 31, 1951 c, PIERCE 2,562,507

SMOKE ELIMINATING APPARATUS 4 Sheets-Sheet 3 Filed June 18, 1947INVENTOR.

CQA/WHV PIERCE July 31, 1951' v c PIERCE 2,562,507

SMOKE ELIMINATING APPARATUS Filed June 18, 1947 4 Sheets-Sheet 4 V A I,e l as ATTORNEY Patented July 31, 1951 UNITED STATES PATENT F F ICE2,562,507 SMQKE ELIMINATING APPARATUS Conway Pierce, Detroit, Mich.

Application tune 18, 1947, Serial No. 755,296 16 Claims. (01. 236-15)means in response to the density of the smoke,

discharged from the fuel burning equipment.

Another feature of this invention is to incorporate in the controlapparatus a timing device which is rendered operative by the smokedetector means to connect the fluid supply means to the combustion Zoneof the fuel burning equipment and maintains this connection for apredetermined period of time, regardless of the condition of the smokdetector means. This arrangement assures effective elimination of the,

smoke and minimizes repeated starting and stopping of the apparatus.

Still another feature of this invention is to provide an arrangementwherein the fluid supplied to the combustion zone may be supplied fromareas within the combustion chamber or may be supplied from theatmosphere exteriorly of the chamber, or in some instances, may be takenfrom both places. By supplying air to the combustion zone which iscollected from areas within the chamber, a minimum loss ofheat resultsbecause the amount of air to the furnace is not thereby increased with aconsequent increase of heat losses in the exit flue gases.

A further object of this invention is to provide smoke abatementapparatus having two or more fluid supply devices, and having means forsuccessively operating the devices in response to the production ofsmoke in the combustion chamber.

A still further object of this invention is to provide apparatus of thetype set forth in the preceding paragraph having means for delaying theoperation of the second device for a predetermined period of time afterthe first device is started.

The foregoing as well as other objects will be made more apparent asthis description proceeds, especially when considered in connection withthe accompanying drawings, wherein:

Figure 1 is a diagrammatic sectional elevational view showing fuelburning equipment embody- .ing smoke abatement apparatus constructed inaccordance with this invention;

Figure 2 is a wiring diagram of the arrangement shown in Figure l;

Figure 3 is a diagrammatic sectional elevational view of a modifiedconstruction;

Figure 4 is a wiring diagram for the arrangement shown in Figure 3;

Figure 5 is a diagrammatic view of another embodiment of the invention;

Figure 6 is a diagrammatic sectional elevational view of a furtherembodiment of this invention; and

Figure 7 is a wiring diagram for the arrangement shown in Figure 6.

Each of the several embodiments of this invention about to be describedare applicable to practically an type of fuel burning equipment in whichimproper combustion results in the production of smoke. Also provisionis made in each of the several modifications illustrated herein forintroducing fluid into the combustion zon of the equipment in responseto the density of the smoke generated by the equipment. The introductionof fluid to the combustion zone of the fuel burning equipment creates aturbulence in the combustion chamber and supplies additional air to theregion in which combustion originates. This additional air materiallyaids combustion and is supplied in sufficient quantities to assuresubstantially complete burning of the smoke or unburned gases in thecombustion chamber, so that very little or no perceptible amount ofsmoke or unburned gases escape from th combustion chamber through theflue usually provided for this purpose.

As will be more fully hereinafter set forth, the fluid or air may besupplied to the combustion zone from the atmosphere exteriorly oi thechamber, or may be supplied to the combustion zone from the remote areasin the chamber proper. In fact the supplemental air may, under certainconditions, be taken both from the atmosphere eXteriorly-of the chamberand from points within the chamber. The advantage of supplying thesupplemental air from a region within the chamber is that the quantityof excess air is not increased by the process and th heat losses carriedaway'to the flue in the form of sensible heat is kept at a minimum. I

With the above in view, reference is now made more in detail to theembodiment shown in Figures 1 and 2 of the drawings. Referring first toFigure l of the drawings, it will be noted that the reference numeral 10indicates a conventional type of coal burning furnace having acombustion chamber H and having a combustion zone indicated generally bythe reference numeral 12. In accordance with orthodox practice, theproducts of combustion are discharged from the chamber I I through aflue l3 extending from the furnace II) in communication with the chamberH. In the normal operation of a furnace of the above general type, allof. the gases are not thoroughly burned due to the presence ofinsufiicientair in the combustion zone 42, and these gases are releasedthrough the flue IS in the form of smoke, which for the purpose of thisdescription is .considered the gaseous products of combustion madevisible by small particles of carflue.

bon suspended therein. The density of the smoke passing upwardly throughthe flue depends upon the number of particles of carbon suspendedtherein, which in turn depends on the efficiency at which combustiontakes place in the zone l2. The particles of carbon suspended in thesmoke or roducts of combustion eventually settle out in the form ofsoot, and this, of course, is very objectionable.

In order to increase the elficiency of combustion in the zone |2 of thechamber sufficiently to avoid the production of smoke, provision is madeherein for introducing air and steam into the zone l2. In the presentinstance air is introduced into the chamber II from the atmosphereexteriorly of the latter through a tube l4 extending through one sidewall of the furnace l and positioned with the delivery end directlyopposite the zone |2. Air is induced to flow through the tube I4 intothe combustion chamber by discharging a stream of steam through the tubeM. The steam is discharged into the entrant end of the tube by a jet l5spaced axially outwardly from the supply end of the tube a suflicientdistance to enable the entrance of air into the tube and connected to asuitable source of supply (not shown) by a conduit IS. The flow of steamfrom the source of supply to the jet is controlled by a conventionaltwo-way valve suitably supported in the conduit l6 between the jet l5and the source of supply.

The valve I1 is automatically operated in response to the density of thesmoke passing through the flue l3. The means for accomplishing the aboveresult comprises a source of illumination I8 and a light sensitive unitI9, respectively suitably supported at opposite sides of the The sourceof illumination |8 is electrically connected to a source of electricenergy by a circuit 2| having a manually operable switch 22 therein. Thelight sensitive unit I3 may be any one of a number of orthodox unitsavailable to the trade and need not be described in detail herein. Itwill sufiice to point out that the unit l9 comprises a photoelectriccell 23 and a relay switch 24.

The above arrangement is such that the pho toelectric cell 23 isenergized by rays of light projected across the flue [3 by theilluminating device l8, and thereby maintains the relay switch 24 in itsopen position. On the other hand, when the beam of light emitted by thedevice It is interrupted or substantially diminished by the density ofthe smoke passing through the flue, the photoelectric cell isdeenergized, and the relay switch 24 is closed. Referring again toFigure 2 of the drawings, it will be noted that the photoelectric cellis connected to the source 20 of electrical energy by an operatingcircuit 25 having a manually operable switch 26 therein. In

practice the switch 26 is located in close proximity to the switch 22,and both switches are normally closed when the apparatus is in itsoperative condition.

The operating circuit 25 also includes a solenoid 21 having a coil 28connected in series in the circuit 25 and having an armature 29 in thecoil operatively connected to the valve IT. The valve I1 is normallyclosed, and is moved to its open position by the armature 29 when thecoil 28 of the solenoid is energized by the operating circuit 25.

The operating circuit is controlled by an electrically operated timer30, which also may be any one of the standard types available to thetrade, and therefore, is not described in detail herein. It will sufficeto point out that the timer is of the automatic resetting type having anelectric motor 3| for operating the timing means 32 and having a relayswitch 33 connected in series in the operating circuit 25. In accordancewith conventional ractice, the switch 33 is closed by the timer as soonas the motor 3| is operated to start the timing means 32. The means 32may be previously set in accordance with orthodox practice to correspondto a predetermined time interval. When this time interval expires,operation of the motor 3| is discontinued and the switch 33 is not onlyopened, but the timing means is automatically reset to its zero orinitial starting position.

The timing device briefly described above is energized by a controlcircuit 34 including the motor 3| oi the timing device, and alsoincluding the relay switch 24. It follows, therefore, that when therelay switch 24 is closed by the presence of smoke in the flue I3, themotor 3| in the timer is started, and the switch 33 is closed. Closingof the switch 33 in the timer 30 energizes the coil 28 of the solenoid21 and operates the armature 29 to open the valve As stated above,opening of the valve introduces steam and air into the combustion zone|2 in the chamber The introduction of this fluid into the chamberproduces a turbulence in the chamber, so that air from remote areas inthe chamber is also circulated through the combustion zone l2. Thisturbulence also causes the smoke which has accumulated in the chamber |2to pass or circulate through other parts of the combustion zone wherethere is sufficient air for burning. The unburned smoke and gases arethereby quickly burned and pass from the furnace as a smokeless product.

When the density of the smoke passing through the flue between the lightsource l8 and light sensitive unit l9 diminishes to such an extent as topermit the beam of light from the source to again energize thephotoelectric cell 23, the switch 24 is opened. At this 'point it isimportant to note that the control circuit 34 is so connected with theoperating circuit 25 that both the motor 3| and switch 33 are connectedin parallel relation with the relay switch 24. Thus the solenoid 21remains energized or, in other words, the valve remains open until bothswitches 24 and 33 are opened. Accordingly,

should the switch 24 open before the timing means 32 on the timer 30reaches the preselected setting, the motor 3| continues to operate, andthe switch 33 remains closed until the timer completes its cycle ofoperation. Thus the introduction of fluid into the combustion chamber iscontinued until the timer relay switch 33 is opened. It follows from theabove that the operating circuit is maintained closed by the timer 30for a predetermined length of time, regardless of the condition of therelay 24, and this is highly desirable in that it prevents constantfluctuation or repeat operation of the apparatus.

The embodiment of the invention shown in Figures 3 and 4 of the drawingsdiffers from the above described arrangement in that a blower 35 isprovided for supplying air to the combustion chamber The blower 35 isdriven by an electric motor 36 of suitable design and the latter isconnected to a power circuit 31 including a switch 38. The switch 38takes the place of the valve shown in Figure 2 of the drawings,

The solenoid 21 is operated in response to the density of the smokepassing through the flue I3 by the same circuit arrangement shown inFigure 1. Accordingly corresponding parts of the two embodimentsdescribed above are indicated by the same reference numerals.

The timer as and associated parts are replaced in the embodiment of theinvention shown in Figure 5 'of the drawings by a fluid-pressureoperated timing system designated generally by the numeral ill. Thissystem comprises a number of parts among which are a displacement pumpil, a fluid motor 42, a control valve 43 and a reservoir M. The pump 4|may be operated by any suitable type of prime mover, and has a piston itslidably supported in a cylinder 53 having the end at the pressure sideof the piston connected to the reservoir through a check valve 41. Theend aforesaid of the pump cylinder also has a fluid connection with thecontrol valve 43 and a check valve E8 is included in the aboveconnection to prevent fiow of fluid from the valve to the pump cylinder.

The fluid motor 32 has a piston 39 slidably mounted in a cylinder 59connected at its upper end to the reservoir by a fluid return conduit 5!and connected at its lower end to the control valve by a conduit 52. Thelower end of the cylinder 58 is also connected to the fluid returnconduit 5! by a conduit 53 including a metering valve 5%. The piston 48has a mechanical connection with one end of a lever 55 by a rod 56 ex"tending downwardly from the piston 49 through an opening in the lowerend of the cylinder 5!! and the other end of the lever 55 is pivoted toa suitable fixed support 5?. The lever 55 is connected intermediate theends to a valve l1 identical in purpose to the correspondingly numberedvalve in the first embodiment of the invention. The valve ii? isnormally urged to its closed position by a coil spring 58 having thelower end bearing on the lever intermediate the ends of the latter andhaving the upper end engaging an abutment 59 fixed to the upper end of avertical rod GB. The rod extends axially through the coil spring and isconnected to the valve ii. The general arrangement is such that the coilspring 53 tends to maintain related positions between the lever 55, rod55 and valve ll, such that when the lever 55 is down, the valve I! isclosed by the spring 58.

The valve 43 is normally held in its closed position or in a positionwherein the portion of the power cylinder 50 below the piston 59 isclosed to the discharge side of the pump cylinder 4!, The valve 43 isoperated by a solenoid 2'! identical to the correspondingly numberedsolenoid in the operating circuit of the first embodiment of thisinvention. The same type of operating circuit is provided in Figure 5 ofthe drawings and is automatically controlled in response to the densityof the smoke passing through the flue by the same instrumentali iesdescribed in connection with the arrangement disclosed in Figures 1 and2 of the drawings.

In operation when the solenoid 2'! is energized the valve 33 is openedpermitting. fluid under pressure to how from the discharge side of thepump 1 to the lower end of the power cylinder 56 below the piston 49. Asthe piston 49 is moved upwardly in the cylinder 50 by the pressure ofthe fluid acting on the bottom surface of the piston, the free end ofthe lever 55 is swung upwardly compressing the spring 5'8 and therebyopening the valve I? to admit steam and air into the combustion chamberH through the tubes M.

Assuming now that the smoke condition in the combustion chamber II hasbeen relieved or eliminated, and that the light sensitive cellcontrolled relay 24 is again opened, it will be noted that the solenoid27 is deenergized and the valve -"$3 is again closed. However, the valveI1 is prevented from closing by the rod 6e and remains open uhtil thepressure in the cylinder 58 below the piston t3 drops sufiiciently toenable downward movement of the piston by the spring 58. In the presentinstance the rate at which fiuid escapes from the lower end of thecylinder 50 is regulated by the needle valve 54 and, as a consequence,any desired lag between opening of the relay 24 and closing of the valveI! may be provided. Of course if the relay 2 again closes before thevalve l l is closed, the valve 43 opens, and closing of the valve I7 isfurther delayed. Thus effective elimination of the smoke in thecombustion chamber ii is assured, and the objectionable fiuctuatingaction of the control mechanism is avoided. V

In Figures 6 and '7 of the drawings, I have shown a dual stage smokeabatement system in connection with a power boiler and furnace equippedwith an overi'eed coal stoker of the chain grate type. This type ofequipment is well known in the art, and need not be described in detail.For the purpose of this description, it will suffice to point out thatthis furnace is also provided with a combustion zone I? in the chamber 1l and with a flue i3 through which the products of combustion aredischarged.

Referring now more in detail to Figure 7 of the drawings, it will benoted that the reference numeral 538 indicates the first stage of thesmoke abatement apparatus, and the numeral Bl designates the secondstage. The operation of the two stages is controlled by a common lightsource I 8 and a common light sensitive unit 19 positioned at oppositesides of the path of the products of combustion flowing from thecombustion chamber II through the flue 13. These instrumentalities arethe same as those previously described in connection with the abovemodifications of this invention, and operate in an identical manner.

Actually, the stage 6%! corresponds to the embodiment shown in Figures 3and 4 of the drawings, and similar parts are indicated by the samereference characters. However, in Figure 6 of the drawings, the intakeside of the blower 35 is connected to a conduit 62 which extends intothe boiler setting and is positioned to draw gas from the last pass 63of the boiler. The discharge side of the blower is connected to deliverytubes 65 by a supply conduit 65 and these tubes are positioned todischarge the gases into the combustion zone 1! of the furnace. Aspointed out in connection with the modification shown in Figures 3 and 4of the drawings, the blower 35 is operated by an electric motor. 35connected in an electric supply circuit 3'! and controlled by a switch38 in aid circuit. The switch 38 is operated by a solenoid 27 and thelatter in turn is operated in response to the density of the smokepassing upwardly through the flue l3. As further pointed out in thedescription of the first embodiment of this invention, the coil 28 ofthe solenoid 21 is electrically connected in an op erating circuit 25including the switch 33 of the timer 3!], and the motor 3! for the timeris electrically connected in both the operating circuit 25 and controlcircuit 3 3. The arrangement is such that should the relay switch 24open prior to completion of the operation of the timer, the lattercontinues to operate under power received from the operating circuit 25.

The second stage of the smoke abatement system comprises a plurality ofjets 66 corresponding to the jets l and adapted to inject air and steaminto the combustion chamber through one or more sides of the furnace inthe same manner described in connection with Figures 1 and 2 of thedrawings. The flow of steam to the jets 66 is controlled by a valve [1and the latter is operated by a solenoid 2T identical to the solenoid21. The coil 28 of the solenoid 21' is connected in an operating circuit25 in parallel with the coil 28 of the solenoid 21 and is operated bythe relay 24 through a second timer 36' identical to the timer 30. Theswitch 33 of the timer 38' is electrically connected in the operatingcircuit 25' in parallel with the timer switch 33, and the motor 3| forthe second timer 30' is connected in the operating and control circuitsso as to continue operation of the timer until it completes its cycle,regardless of the condition of the relay switch 24.

As shown in Figure '7 of the drawings, a time delay relay switch 61 isconnected in series with the timer motor 3|, and a relay switch 68 isconnected in series with the timer motor 3 I. The switch 68 is normallyclosed and the actuating coil of this switch is connected in series withthe switch 33' of the timer 30, so that when the switch 33' is closed toenergize the solenoid 21', the switch 68 is opened. The time delayswitch 81 may be of any suitable design available to the trade, and theactuating coil thereof is shown in Figure 7 as connected in parallelwith the timer 30. As a result, the coil for the switch 61 is energizedas soon as the operating circuit 25 is closed by the timer switch 33.However, the closing of the switch 6! is delayed for some time, as willbe presently described.

In operation of the modified construction shown in Figures 6 and 7 ofthe drawings, it will be noted that when the density of the smokepassing through the flue l3 exceeds a value sufiicient to interrupt thelight beam directed by the source l8 toward the light sensitive unit 19,the relay switch 24 closes and starts the timer 3!]. As a result theswitch 33 closes the operating circuit 25, and the switch 38 is closedby the solenoid 21 to operate the blower 35. The blower draws heated gasfrom the last pass of the boiler and delivers it to the combustion zonel2 of the chamber l l to improve the efficiency of the come bustiontaking place in this zone.

In most instances the above procedure will eliminate smoke productionwith negligible heat loss. However, in some instances, the production ofsmoke in the furnace may be so severe. that it cannot be eliminated bythe above operation. In such cases the time delay switch 61 closes andstarts operation of the timer 30', which like the timer 30, has beenpreset to operate for a preselected period of time. 33, of course,closes the circuit 25' to the solenoid 2'1 and causes the latter to openthe valve I1. Thus steam and air from the outside of the furnace aresupplied to the combustion zone [2 to supplement the gases supplied bythe blower and combustion in the zone I2 is immediately improved.Attention is called to the fact that closing of the switch 33 alsoenergizes the relay coil for the switch 68 and opens the latter todiscontinue operation of the motor 3| for the timer The switch,

30, so that the blower will continue to operate during the period thesecond stage 6| of the system is in operation.

When the timer 30' completes its operation and the timing means is resetto its zero or initial starting position, the switch 33 is operated toopen the operating circuit 25'. As a result the solenoid 27' isdeenergized and the valve I! is again closed. Opening of the operatingcircuit 25' by the timer switch 33 also deenergizes the coil of therelay switch 68 and permits the latter to again close. This enables thetimer motor 3| to continue its operation until the preselected timingperiod is expired, whereupon the switch 33 is opened and operation ofthe blower 35 is discontinued. Opening of the switch 24 also serves todeenergize the coil for the time delay relay switch 61 and permits thelatter to open, so that the timer 30 is again disconnected from thecontrol circuit 34 of the system. Thus both stages of the system areagain ready to operate on demand from the smoke detector and the cyclerepeats for another preselected period Of time when smoke is againdetected.

The second stage 6| will not start operating until the first stage 60 isoperated for a length of time determined by the time delay switch 61.Therefore, the second stage 6| may be considered as an emergency systemwhich is called upon to afford protection only in severe cases, or inthe event of failure of the first stage.

What I claim as my invention is:

1. Apparatus for substantially eliminating the production of smokeresulting from improper combustion of a fuel in a chamber having anoutlet through which the products of combustion pass, said apparatuscomprising means for supplying a smoke reducing fluid to the combustionzone in the chamber, an electric circuit having a switch connected inseries in said circuit, a solenoid for operating the fluid supplyingmeans and having a coil connected in series in said circuit, means foropening and closing the switch including an electrically operated timerof the automatic resetting type having provision for delaying opening ofthe switch for a predetermined time, a control circuit for the timer,and means controlled by the density of the smoke discharged from thecombustion chamber for closing the control circuit upon an increase inthe smoke density above a predetermined value and for opening thecontrol circuit upon a decrease in smoke density below saidpredetermined value.

2. Apparatus for substantially eliminating the production of smokeresulting from improper combustion of a fuel in a chamber having anoutlet through which the products of combustion pass, said apparatuscomprising means for supplying a fluid to the combustion zone in thechamber, electrically operated means for controlling the operation ofthe fluid supplying means and including an electric operating circuithaving a switch therein, an electric control circuit having means forclosing said switch, a switch in the control circuit controlled by thedensity of the smoke discharged from the chamber for closing the switchin the control circuit upon an increase in the smoke density at theoutlet above a predetermined value and for opening the switch in thecontrol circuit at the outlet upon a decrease in the smoke density belowsaid predetermined value, and means for delaying opening of the switchin the operating circuit for a predetermined period of time.

3. Apparatus for substantially eliminating the production of smokeresulting from improper combustion of a fuel in a chamber having anoutlet through which the products of combustion pass, said apparatuscomprising an electric control circuit having a relay, means also in thecontrol circuit responsive to an increase in smoke density at the outletabove a predetermined value to close the relay and responsive to adecrease in smoke density at the outlet below said predetermined valueto open said relay, means for supplying a smoke reducing fluid to thecombustion zone in the chamber in response to closing of the relay and atimer renderedoperative by the closing Of the relay and having means forcontinuing the supply of fluid to the chamber for a preselected periodof time independently of the operation of said relay.

4. Apparatusfor substantially eliminating the production of smokeresulting from improper combustion of a fuel in a chamber having anoutlet through which the products of combustion pass, said apparatuscomprising an electric control circuit having a switch, means also inthe control circuit responsive to an increase in smoke density at theoutlet above a predetermined value to close the switch and responsive toa decrease in smoke density at the outletbelow said predetermined valueto open the switch, means for supplying fluid to the combustion zone ofthe chamber including an operating electric circuit, a switch in theoperating circuit shunting the switch in the control circuit, and atimer for operating the second named switch including electricallyoperated mechanism connected in the control circuit.

5. Apparatus for substantially eliminating the production of smokeresulting from improper combustion of a fuel in a chamber having anoutlet through which the products of combustion pass, said apparatuscomprising an electric control circuit having a relay movable to itsopen and closed positions in response to the density of the products ofcombustion discharged from the chamber, an electrically operated blowerhaving the discharge side communicating with the chamber and included inan electric supply circuit having a switch, an operating electriccircuit including means for operating the switch in the supply circuit,and a timer having a switch shunting the switch in the control circuitand having mechanism for operating the timer switch connected in thecontrol circuit.

6. Apparatus for substantially eliminating the production of smokeresulting from improper combustion of a fuel in a chamber having anoutlet through which the products of combustion pass, said apparatuscomprising an electric control circuit having a relay movable to itsopen and closed positions in response to the density of the products ofcombustion discharged from the chamber, valve controlled means forsupplying fluid to the combustion zone in the chamber, means for openingand closing the valve in response to the operation of the relay, andfluid pressure operated means for delaying closing of said valve for apredetermined period of time regardless of the condition of said relay.

'7. Apparatus for substantially eliminating the production of smokeresulting from improper combustion of a fuel in a chamber having anoutlet through which the products of combustion pass, said apparatuscomprising an electric control circuit having a relay, means also in thecontrol circuit responsive to an increase in the smoke density at theoutlet above a predetermined value to close the relay and responsive toa decrease in smoke density at the outlet below said predetermined valueto open the relay, means for supplying fluid to the combustion zone ofthe chamber, means for operating the supply means in response to closingof the relay including an operating circuit having a solenoid, a switchconnected in the operating circuit in series with the solenoid andshunting the switch in the control circuit, and an electrically operatedtimer connected in the control circuit for closing and opening theswitch in said operating circuit.

8. Apparatus for substantially eliminating the production of smokeresulting from improper combustion of a fuel in a chamber having anoutlet through which the products of combustion pass, said apparatuscomprising an electric control circuit having a relay switch movable toits open and closed positions in response to the density of the productsof combustion discharged,

from the combustion zone, means for supplying a fluid to the combustionzone in the chamber including an operating circuit having two solenoidsconnected in parallel in the operating circuit, first and secondswitches in the operating circuit for respectively controlling thesolenoids, means for successively closing the switches in response toclosing of the relay switch, and means for delaying closing of thesecond switch for a predetermined period of time after closing of thefirst switch.

9.- Apparatus for substantially eliminating the production of smokeresulting from improper combustion of a fuel in a chamber having anoutlet through which the products of combustion pass, said apparatuscomprising an electric control circuit having a relay switch movable toits open and closed positions in response to the density of the productsof combustion discharged from the combustion zone, means for supplying afluid to the combustion zone in the chamber including an operatingcircuit having two solenoids connected in parallel in the operatingcircuit, first and second switches in the operating circuit forrespectively controllingthe solenoids, a timer for closing the firstswitch in response to closing of the relay switch and for maintainingsaid first switch closed for a predetermined period of time, a secondtimer for closing the second switch, and time delay means in response toclosing of the relay switch for initiating the operating of the secondtimer.

10. Apparatus for substantially eliminating the production of smokeresulting from improper combustion of a fuel in a chamber having anoutletthrough which the products of combustion pass, said apparatuscomprising an electric control circuit having a relay switch movable toits open and closed positions in response to the density of the productsof combustion discharged from the combustion zone, means for supplying afluid to the combustion zone in the chamber including an operatingcircuit having two solenoids connected in parallel in the operatingcircuit, first and second switches in the operating circuit forrespectively controlling the solenoids, a timer for closing the firstswitch in response to closing of the relay switch and for maintainingsaid first switch closed for a predetermined period of time, a secondtimer for closing the second switch in response to closing of the relayswitch and for maintaining the secondswitch closed for a predeterminedperiod of time, and means for delaying operation of the second timer toclose the second switch for a predetermined period of time after closingof the first switch.

11. Apparatus for substantially eliminating the production of smokeresulting from improper combustion of a fuel in a chamber having anoutlet through which the products of combustion pass, said apparatuscomprising an electric control circuit having a relay switch movable toits open and closed positions in response to the density of the productsof combusiton discharged from the combustion zone, means for supplying afluid to the combustion zone in the chamber including an operatingcircuit having two solenoids connected in parallel in the operatingcircuit, first and second switches in the operating circuit forrespectively controlling the solenoids, a timer for closing the firstswitch in response to closing of the relay switch and for maintain-- ingsaid first switch closed for a predetermined period of time, a secondtimer for closing the second switch in response to closing of the relayswitch and for maintaining the second switch closed for a predeterminedperiod of time, means for delaying operation of the second timer for apredetermined length of time, and means for interrupting the timingcycle of the first timer in response to operation of the second timer toclose the second switch.

12. Apparatus for substantially eliminating the production of smokeresulting from improper combustion of a fuel in a chamber having anoutlet through which the products of combustion pass, said apparatuscomprising an electric control circuit having a relay switch movable toits open and closed positions in response to the density of the productsof combustion discharged from the combustion zone, means for supplying afluid to the combustion zone in the chamber including an operatingcircuit having two solenoids connected in parallel in the operatingcircuit, first and second switches in the operating circuit forrespectively controlling the solenoids, a timer for closing the firstswitch in response to closing of the relay switch and for maintainingsaid first switch closed for a predetermined period of time, a secondtimer for closing the second switch in response to closing of the relayswitch and for maintaining the second switch closed for a predeterminedperiod of time, means for delaying operation of the second timer toclose the second switch for a predetermined period of time after closingof the first switch, and means for interrupting the timing cycle of thefirst timer in response to operation of the second timer.

13. Apparatus for substantially eliminating the production of smokeresulting from improper combustion of a fuel in a chamber having anoutlet through which the products of combustion pass, said apparatuscomprising an electric control circuit having a relay switch movable toits open and closed positions in response to the density of the productsof combustion discharged from the combustion zone, means for supplying afluid to the combustion zone in the chamber including an operatingcircuit having two solenoids connected in parallel in the operatingcircuit, first and second switches in the operating circuit forrespectively controlling the solenoids, a timer for closing the firstswitch in response to closing of the relay switch and for maintainingsaid first switch closed for a predetermined period of time, a secondtimer for closing the second switch in response to closing of the relayswitch Number and for maintaining the second switch closed for apredetermined period of time, means for delaying operation of the secondtimer to close the second switch for a predetermined period of timeafter closing of the first switch, and a normally closed relay switchfor also controlling the operation of the first timer and connected inseries with the second switch for successively stopping and starting thefirst timer upon closing and opening the second switch.

14. Apparatus for substantially eliminating the production of smokeresulting from improper combustion of a fuel in a chamber having anoutlet through which the products of combustion pass, said apparatuscomprising an electric control circuit having a relay switch movable toits open and closed positions in response to the density of the productsof combustion discharged from the combustion zone, first and seconddevices for independently supplying fluid to the combustion zone, andmeans responsive to closing of the relay switch for successivelyoperating said devices.

15. Apparatus for substantially eliminating the production of smokeresulting from improper combustion of a fuel in a chamber having anoutlet through which the products of combustion pass, said apparatuscomprising electric control circuit having a relay switch movable to itsopen and closed positions in response to the density of the products ofcombustion discharged from the combustion zone, first and second devicesfor independently supplying fluid to the combustion zone, and means fordelaying the operation of the second device for a predetermined periodof time after the operation of the first device.

16. Apparatus for substantially eliminating the production of smokeresulting from improper combustion of a fuel in a chamber having anoutlet through which the products of combustion pass, said apparatuscomprising means for supplying a smoke reducing fluid to the combustionzone in the chamber, an electric operating circuit having a switchconnected in series therein, means in said circuit for operating thefluid supply means and controlled by said switch, a timer for openingand closing said switch, a control circuit having means for operatingthe timer, a switch in the control circuit for opening and closing thecontrol circuit, and means controlled by the density of the smokepassing through the outlet for closing the switch in the control circuitupon an increase insmoke density above a predetermined value and foropening the switch in the control circuit upon a decrease in the smokedensity below said predetermined value.

CONWAY PIERCE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date McDonald Dec. 27, 1898 Holby Apr. 9,1940 Adams Mar. 10, 1942 FOREIGN PATENTS Country Date Germany Mar. 27,1907 Great Britain Mar, 11, 1929 Great Britain Dec. 3, 1934 Number

